Process for the synthesis of hydrocarbons



E. F. PEVERE ET A, '2,418,899 PROCESS FOR THE SYNTHESIS OF HYD ROCARBONSFiled 0G12. 24,' 1945 pril l5, '1947.

Patented Apr. 15, 1947 POCESS FOB THE SYNTHESIS'OF HYDRCAI'LBONS` pany,New York, NY

..` a corporation of Delasppueauoocmser 24, 1945, serial No. 624,292

1 Our invention relates to the synthesis'of hydrocarbone, and especiallyto an improved'process for synthesizing hydrocarbons ofmotor fuel rangeby the hydrogenation of carbon oxides.

The present application isa continuation-inpart of our co-pendingapplication, S. N. 461,852, led October 13, 1942, for Process for thesynthesis of hydrocarbons.

The synthesis of hydrocarbons by the hydrogenation of carbon monoxidehas been operated lar theory by which it may operate.

on a-commercial scale for a number of years, but

this process has had certain disadvantages, particularly in thevcharacter of the hydrocarbons produced. The motor fuels obtained by thisprocess have not been comparable in anti-knock properties to motor fuelsobtainable from petroleum fractions, and have generally had octanenumbers considerably vbelow straight run and thermally crackedgasolines. i

An object of the present invention is to provide a process for thehydrogenation of carbon oxides to produce motor fuel hydrocarbons ofimproved anti-knock characteristics.

Another object oi' our invention is to provide an improved reactionmixture for the vapor phase catalytic hydrogenation of carbon oxides toproduce increased yields of hydrocarbons.

A further object of our invention is to provide a suitable continuous.cyclic process for eiecting our improved hydrogenation reaction.

Other objects and advantages of our invention will be apparent from thefollowing description.

In accordance with the present invention, the reactant mixture for thehydrogenation contains, in addition to hydrogen and a carbon oxide, asubstantial proportion of a hydrocarbon component comprising essentiallybranched chain hydrocarbons. The provision of a branched chainhydrocarbon in the reaction mixture-increases the yield of hydrocarbonsof motor fuel range and above, and thus effects a marked improvement inthe volumetric eiliciency of the catalytic unit. The use of a branchedchain hydrocarbon in the reaction mixture also modies thecharacteristics of the reaction products, and effects a markedimprovement in the anti-knock characteristics of the motor fuel rangehydrocarbons. It is believed that the branched chain hydrocarbon reactswith methylene radicals at the catalyst surface to produce branchedchain hydrocarbons of higher molecular weight, rather than essentiallystraight chain hydrocarbons, such as are produced from carbon monoxideand hydrogen alone. However, it is to be understood 9 claims. (c1.26o-449.6)

that our invention is not limited to any Any branched chain hydrocarbonof lower molecular weight than the desired reaction product may beemployed in our process, but we prefer to -use .a branched chainhydrocarbon which is in the vapor state under the hydrogenationconditions employed. Isobutane, isobutylene, isopentane. themethylbutenes andmethyipentenes, 2,2-dimethylbutane, and2,3-dimethylbutane are examples of ,hydrocarbons of the preferredvolatility range.

When effecting the reaction with a liquid phase in contact with thecatalyst, higher boiling branched chain hydrocarbons auch asdiisobutylene, tri-isobutylene, andthe corresponding par- 'aillns may beemployed A mixture of such hydrocarbons inay be employed if desired, butthe recycling of unreacted branched chain hydrocarbon'in thesubstantialabsence of straight chain motor fuelf range.

hydrocarbons willbe simplifiedI if only a single branched chainhydrocarbon is 'used for this purpose. Although any branched chainhydrocarbon will, be ,operative in our process we prefer to useisoparafnns of 4 to 6 carbon atoms, and our invention will be.speciilcally illustrated with respect to the use of ,isobutana Theamount of hydrocarbon to be incorporated in the reaction mixture may bevaried over relatively wide limits, depending on the particularhydrocarbon employed, and the nature of the synthetic hydrocarbons to beproduced. Alarser amount of hydrocarbons may be employed when thecatalyst and reaction conditions are chosen for the production of awidel range product, including high molecular weight constituents, thanis desirable when the synthesis conditions are designed to produceprimarily light hydrocarbons of It is desirable to employ at least 5 molper cent of isobutane, based on the carbon -oxide in the reactionmixture, -and correspondingamounts of other branched chain hydrocarbons.Amounts of 5 to 15 mol per cent are suitable for obtaining asubstantially modified reaction product. However, a large excess of thebranched chain hydrocarbon, e. g., -1000 mol per cent, may be employedto minimize the formation of the usual carbon oxide hydrogenatlonproducts.

carbon in the reaction mixture, the hydrogenation reaction may beeilected in accordance with prior practices in the art. Either carbonmonoxide or carbon dioxide may be employed, using thev known ratios ofhydrogen to carbon oxide in each case. However, carbon monoxide isusually to be a temperature lof 1200-1500# F. carbon monoxide-hydrogenpreferred. and further discussion herein will refer speciilcally tocarbon monoxide.

The usual catalysts. comprising metals of the eighth group of theperiodic system, together with activating constituents, such asaluminum, magnesium, thorium, their oxides, and the like may be employedin our process. Any catalyst which is effective for the reaction andhydrogen alone. will be found to be operative 'with the reactionmixtures of the present invention.4 Such catalysts may beprepared,reduced, and conditioned in the usual manner, and may be used in the drystate for a fully vapor phase process. or may be used in the form of aslurry in a v'high boiling hydrocarbon or other liquid carrier.

The temperature and pressure conditions for the reaction may be the sameas those employed with the particular catalyst for the reaction ofcarbon monoxide and hydrogen alone. Temperature of 325 to 550 F., andApreferably 390 to 450 F., or in the range about 325 to 100 F., andpressures up-to 100 atmospheres but preferably from atmospheric toiifteen atmospheres. constitute -suitable conditions with mostcatalysts.

The contact time need not .be modied when incorporating a branched chainhydrocarbon in the reaction mixture, although improved yields of lightmotor fuel fractions maybe obtained in some cases by utilizing asomewhatshorter contact time than would be employed in-the absenceV of ahydrocarbon reactant. i

In order to operate the hydrogenation processes economically, it isdesirablel to recycle the. un-

reacted carbon monoxide and hydrogen, and to utilize vthe methane .andother low molecular weight hydrocarbons which process. The fixed gases,condensable hydrocarbons.. 'may be separated usually preferable to.oxidize the hydrocarbon component to carbon monoxide prior to recycling.

For this purpose, the fixed gases-may be mixed withsteam or otheronzen-containing gas, and passed over a suitable catalyst, such asnickel, at The resulting mixture. after cooling by suitable heatexchange, may then be recycled to the hydrogenation reaction,preferably' of carbon monoxide including the noli--4 4 f tion may besubjected to polymerization. alkylation, or other conventional reactionsfor the production of the higher boiling hydrocarbons. The. alkylationreaction isparticularly advantageous,

however. sincethe separated narrow boiling fraction contains both theisoparafiin and-the oleilns required for the alkylation reaction.

The use of isobutane as the branched chain hydrocarbon in the reactionmixture, and the.

*tionA of xed gases, oxidation of the hydrocarbon content of the xedgases by catalytic reaction with steam at high temperature, and recycleof are produced in the the resulting carbon monoxide-hydrogen mixture,are efected in accordance with conventional procedures. Thisrepresentation, however, isonly diagrammatic, and additional expedientellwhich are commonly employed, such as the use of f activated charcoaladsorbers to effect-,complete recoveryof products from the gas mixture,may alsobe used. In this phase of the process, the

only distinction of'our procedure overprior prac-, tices is theincorporation of 'isobutane in the reaction mixture. A

In order to recover isob,vv taie f romthe reaction product for recycle,the primaryjractionator is operated toseparate propane and propylene 'asoverhead, and toob'tainas a side-outa light liquid hydrocarbon fractioncontaining the butanes and butylene's. The latter fraction is 'then'deIs' butanized, andlthe debutanizer overhead is iractionated tobbtain anisobutane-butene distilfrom-the reaction product and recycled, but it'isbeing mixed with the fresh make-up reactants prior to entering thereaction vessel. This pro-v4 cedure, and other -known expedients forcyclic operation of the hydrogenation process'. may be used inconjunction with our present improvements; and our invention is notlimited to the use of any particular procedures or reactin conditionsfor effecting recycle of carbon monoxide. and hydrogen.

In order to utilize a branched chain hydrocarbon in the reaction mosteconomically, it is also desirable .that the unreacted hydrocarbon berecycled in the process. For this purpose, the particular hydrocarbonemployed may be separated from the light liquidhydrocarbon reactionproduct by conventional methods, such as multiple stage fractionation,azeotropic distillation, and' the like.

One advantageous method of separating an unreacted isoparain comprisesthe recovery -of a fraction containing only the isoparafn and theoleiins of substantially the same-boiling point, reacting the olencontentA of this fraction to produce. higher boiling hydrocarbons,separating the latter, and hydrogeriation reaction. In this type ofoperation, the olen content of the narrow boiling iraclate, which isemployed in the alkylation step -of theprocess.

' The alkylation may be effected in accordance' with any of theusualmethods, utilizing catalystssuch as sulphuric acid, hydrouoricacid,

aluminum chloride, and the like. In the modi` cation illustrated,sulfuric acid is used as the catalyst, and the' reaction and separationof the reaction product are effected in the conventional, manner. Thealkylate' debutanizer overhead supplies recycle.. isobutane for eitherthe alkylation reaction,'the hydrogenationreaction, or both, as j may bedesired. .The make-up isobutane for the process Amay likewise besupplied only to the 't alkylation step, or to .the hydrogenation step,or to both, as desired. Generally, we prefer to supply the .make-upisobutane to the hydrgenation step and utilize most or all 'of therecycle isobutane to supply the large excess desired in the alkylationreaction. The particular distribution of the makeup and recycleisobutane, however, will be determined in-any case by the relativeamounts of .reactants'em'ployed in the hydrogenation and alkylationreactions-' It may be seen that the procedure described aboye has theadvantage of improving the yield andquality of the motor fuelhydrocarbonsprduced in the hydrogenation reaction, and also yieldingadditional motor fuel hydrocarbons of high 'quality f romthegaseousolefins produced in the hydrogenation.

recycling the isoparailin to the The following specic examplelillustrates the vuse of theprocedure described above:

aiample A hydrogenation catalyst comprising cobalt 011s" oxide withminor amounts of manganese, thorium, and magnesium oxides, supported onkieselguhr, and reduced with hydrogen at an increasing temperature from650 to '770 F., is employed for the hydrogenation of carbon monoxide,with and without isobutane in the reaction mixture. The charge rates,essential reaction conditions, and the hydrocarbon yields which areobtained under these conditionsare shown in the table 2. The methodaccording to claim 1 in which the isoparamn is isobutane.

3. The method according to claim 1 in which the isoparaiiin isisopentane.

4. In a catalytic process for synthesizing hydrocarbons by thehydrogenation of a carbon oxide, the method'which comprises continuouslypassing to a reaction zone a reactant feed combelow: prising carbonmonoxide, hydrogen and iso- Char cu. ftJhr. per cu. it. Hydrocarbon geof catalyst Tem- .Space vel yield lha/1,000 era. Pres ity cu. ft. of cun of charge Iure sure' charge/hr' recoverable by Carbon Hydro- Isobuatmper etui of condensation and Monoxide gen tane ca a ys adsorption The C.F. R. M. octane number of the motor fuel fraction in the rst case aboveis only about 45, whereas the octane number of the motor fuel fractionin the second case may be as high as 65, or even higher. If the sulfuricacid alkylate from the isobutane-butene fraction of the hydrogenationproduct is blended with the motor fuel fraction, the octane number ofthe overall-motor fuel produced may be increased to 68, or higher.

It is to be understood, of course, that the above example is merelyillustrative and does not limit the scope of our invention. Otherbranched chain hydrocarbons may be used in the reaction mixture, inplace of isobutane, and the reaction conditions may be modified invarious respects, as pointed out in the preceding discussion. Similarly,other equivalent procedures may be employed for recovering unreactedbranched chain hydrocarbon for recycling to the hydrogenation reaction.In general, it may be said that the use of any equivalents ormodifications of procedure which would naturally occur to those skilledin the art, is included in the scope of our invention. Only suchlimitations should be imposed on the scope of our invention as areindicated in the appended claims.

We claim:

1. In a catalytic process for synthesizing hydrocarbons by thehydrogenation of a carbon oxide, the method which comprises continuouslypassing to a reaction zone a reactant feed comprising carbon monoxide,hydrogen` and isoparafn hydrocarbon having from 4 to 6 carbon atoms permolecule, subjecting the reactant feed in the gas phase to contact witha hydrogenation catalyst comprising a metal of the eighth group of theperiodic system, and a minor amount of a metal oxide having theessential promoting action of thorium and magnesium oxides, effectingcontact between the reactants and the catalyst at a temperature in therange 325 to 550'F. and under a pressure ranging from atmospheric toabout 15 atmospheres, continuously removing from the reaction zone 'astream of reaction products comprising unreacted isoparaffin andsynthesized hydrocarbons. separating unreacted isoparafiin from thereaction products, and recycling said separated isoparaiiin to thereaction zone, the amount of isoparain entering the reaction zone beingat least 5 mol per cent based on the carbon oxide in the reactionmixture.

ing contact between the reactant and the catalyst at a temperature inthe range 350 to 450 F. and under substantially atmospheric pressure,continuously removing from the reaction zone a stream of reactionproducts comprising unreacted isoparain and synthesized hydrocarbons,

separating unreacted isoparaiin from the reaction products, andrecycling said separated isoparaiiin to the reaction zone, the amount ofisoparafiin entering the reaction zone being about 5 t0 15 mol per centbased on the carbon oxide in the reaction mixture.

5. The method according to claim 4 in which the isoparafn is isobutane.

6. The method according to claim 4 in which the isoparailin isisopentane.

7. In a catalytic process for synthesizing hydrocarbons by thehydrogenation of a carbon oxide, the method which comprises continuouslypassing to a reaction zone a reactant feed comprising carbon monoxide,hydrogen and isoparaiiin hydrocarbon having from 4 to 6 carbon atoms permolecule, subjecting the reactant feed in the gas phase to contact withan active synthesis catalyst comprising a metal of the eighth group ofthe periodic system, effecting contact between the reactants and thecatalyst at a temperature in the range about 325 to 700 F. and under apressure ranging from atmospheric to about atmospheres, continuouslyremoving from the reaction zone a stream of reaction products comprisingunreacted isoparaifin and synthesized hydrocarbons, separating unreactedisoparaiiin from the reaction products. and recycling said separatedisoparaihn to the reaction zone, the amount of isoparaflin entering thereaction zone being at least 5 mol per cent based on the carbon oxide inthe reaction mixture.

8. The method according to claim 7 in which the isoparaiiin isisobutane.

9. The method according to claim '7 in which the isoparaln isisopentane.

ERNEST FRANK PEVERE. GEORGE BATES HATCH. EUGENE EDWARD SENSEL.

